Making an old mac 802.11n compliant

my wife has just purchased a new Macbook, which of course has a 802.11n compliant wireless card. However, at home I have an original Core Duo MBP and an old G5 iMac, neither of which are compliant. I am considering buying a Time Capsule for backing them all up at home, and shouldn't imagine backing up over g on the old computers would be too much fun. I have found this dongle on Amazon, as was wondering if it would make my old Macs n capable and work with Time Capsule?

MacRumors attracts a broad audience
of both consumers and professionals interested in
the latest technologies and products. We also boast an active community focused on
purchasing decisions and technical aspects of the iPhone, iPod, iPad, and Mac platforms.